The invention pertains to an anti-skid device for motor vehicles with pneumatic tires, which device has at least two arms at an angle to other each next to the wheel rim when in the installed state, the free ends of the arms being connected to anti-skid means laid around the circumference of the tire, where a fastening device can be used to attach the arms to the wheel.
An anti-skid device of this type is known from Austrian Patent No. 385,243. This also has a bracket, which, when in the installed state, is located next to the outside surface of the wheel and comprises two arms at an angle to each other, the free ends of which are connected to anti-skid means in the form of chains laid around the circumference of the wheel. A coupling device attaches the bracket to the wheel, against which the bracket is held under tension. Rubber belts, which are hooked onto the rim of the wheel, are part of this coupling device. The disadvantages are that not every rim is suitable for accepting the hooks of rubber belts and that this form of attachment to the wheel is not very reliable.
An anti-skid device of the type indicated above, in which a clamping head, which can be attached to a lug nut, is provided to connect the coupling device to the wheel, is also known on the basis of public prior use. In this anti-skid device, the clamping head is connected to the arms of the bracket by a rubber strand, the free ends of which are supported in bushings. One of these bushings is attached to the arms of the bracket, while the other is connected to the clamping head by a connecting piece. The rubber strand exerts a tensioning force on the bracket directed toward the wheel and also absorbs the shifts between the bracket and the clamping head during the rotation of the wheel which are caused by imperfect centering of the installed bracket and especially by the flexing movement of the pneumatic tires as they roll. The disadvantage of this device is the connecting points between the rubber strand and the retaining bushings attached to it, which obviously represent a weak point. As a result of the forces which occur during the use of the anti-skid device, it is possible over the course of time for the rubber strand to work itself loose and break away. The clamping head also works itself loose as a result of the uncentered forces after a relatively short period of operation.
A similar anti-skid device, the bracket of which has a fastening element for connection to a lug bolt, is also known from DE 38 44 494 A1.
A clamping head for attaching an anti-skid device to a lug bolt is also known from, for example, DE 39 10 669 A1. Here the attachment to the lug bolt is off-center and out of balance, and as a result of the one-sided load the snow chain also works itself loose from its anchoring more easily.
An anti-skid device is also known from EP 0,285,903 A1. This device has an adapter part for fastening the anti-skid device to the wheel of the vehicle. The adapter part can be attached by means of clamping heads, which are fastened to the lug bolts.
A task of the invention is to provide an anti-skid device of the type described above which is easy to install and makes possible a reliable attachment of the anti-skid device to the circumference of the tire. This is achieved according to the invention by an anti-skid device.
In an anti-skid device according to the invention, a reliable attachment of the fastening device to the lug nuts or lug bolts is made possible by the adapter part. If the anti-skid device is not needed and is to be removed from the circumference of the tire, the adapter part can remain on the lug nuts. The adapter part can be of a simple design in this case, so that it can be produced at low cost. A single adapter part can be designed in such a way that it can be used on different types of rims such as four-hole rims and five-hole rims. It is also possible to provide different types of adapter parts for different types of rims, especially with respect to the mounting holes and/or with respect to the size of the adapter part, all of which can be used in conjunction with the same coupler.
In an advantageous exemplary embodiment, the anti-skid devices are designed as circumferentially closed, endless strands of chain and are connected by retaining tabs to the arms, a recess being provided in each retaining tab to guide the strand of chain over its assigned tab. To attach the strands of chain in the recesses in the retaining tabs, it is advisable to provide holes in the side walls of these recesses, in which holes chain fastening bolts can be introduced, which are essentially parallel to the surface of the tire, and each of which passes through a link of the chain.
It is also advantageous for the coupling device to comprise a central bolt, on which the arms of the bracket of the anti-skid device are supported. This bolt is connected by ball joint-like connections to the arms at one end and to the minimum of one locking part at the other. It is therefore possible for the movements which occur as a result of the flexing of the tire as it rolls to be absorbed, as a result of which a long service life can be achieved without the occurrence of material fatigue fractures.